The etiology of many types of keratitis is unknown. Likewise the role of the complement system in ocular disease is unknown. Preliminary studies conducted by the investigators have demonstrated that changes in the concentrations of complement components in the aqueous humor and in tears can be correlated with corneal graft rejection, Mooren's ulcer, and forms of keratitis of unknown etiology. These investigations will examine the role of complement in several types of human keratitis and in experimental keratitis produced by both infectious and immunological techniques. Complement components C1, C4, C2, C3 and C9 will be determined in aqueous humor and in tears in a serial fashion. The information derived should elucidate the role of complement in these diseases, may provide a means for early diagnosis of keratitis and corneal graft rejection, and may present clues to the underlying etiology of certain forms of corneal disease.